It is well-known to produce cellulose fibers and other formed products by preparing cellulose solutions in tertiary amine oxides, like N-methyl morpholine-N-oxide (NMMO), optionally containing minor amount of water, extruding the cellulose solutions through spinnerets and coagulating the fibers formed in an aqueous bath followed by at least one washing bath. See for example the U.S. Pat. Nos. 3,447,939, 3,447,956 and 4,211,574.
In AT 401 063 B, it has also been suggested to use non-aqueous fluids in the bath. The cellulose used in these processes has usually a polymerisation degree of not lower than 200 and preferably not lower than 400. The cellulose fibers manufactured from the cellulose-NMMO system according to the above mentioned system normally exhibit a tensile strength of about 15 cN/tex and an elongation at break of about 4-8%. The cellulose fibers intended for clothing purposes must have considerably higher levels of elongation at break, namely over 10% combined with an improved tensile strength. Another disadvantage of cellulose fibers produced by the NMMO system is the too high tendency to fibrilate and to form small balls on the fabric surface, which is also known as pilling.
Furthermore, in the Patent Publication DD-A1-218 121, it has been observed that air gap between the spinneret and the coagulation bath may be reduced if a polyethylene glycol having a molecular weight of 1000 is present in a NMMO cellulose solution.
U.S. Pat. No. 5,047,197 suggests to add a polyethylene glycol having a molecular weight of from about 1.1 milion to about 4.5 milion to a cellulose dissolved in a tertiary amine oxide to improve the flow rate through a spinning nozzle.
WO 96/14451 discloses the use of a polyalkylene imine derivate to stabilize a shaped body derived from cellulose regenerated by the amino-oxide process and WO 86/05526 discloses the possibility to add a number of polymers to a dissolution of lignocellulose materials in a tertiary amino oxide. Thus, none of these references presents a solution of the disadvantages earlier mentioned.
U.S. Pat. No 4,246,221 discloses a NMMO process for the manufacture of cellulose fibers with improved strength. However, the application of the fibers in fabric industry is rather limited due to their wet fibrillation tendency.
Therefore, one object of the present invention is to essentially improve the general properties, like dry strength, wet strength, elongation and to reduce the fibrillation of a cellulose shaped product produced by a tertiary amine oxide process in order to make the fibers more useful, e.g. for textile fabrics.
Another object of the invention is to be able to regulate and to control the water absorption properties of the product, such as retention, absorbed water amounts, and absorption speed.
These and other objects have been met by the method of the present invention.